wifi: ath12k: Use skb->len for dma_unmap_single() length parameter

wifi: ath12k: Use skb->len for dma_unmap_single() length parameter

During dma_unmap_single() for extended skb, the driver currently uses
sizeof() of the corresponding structure. When the allocation size changes,
one of the parameters of dma_unmap_single() needs to be updated everywhere.
Improve code readability by using skb->len instead of sizeof() the structure.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.4.1-00199-QCAHKSWPL_SILICONZ-1
Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3

Signed-off-by: P Praneesh <praneesh.p@oss.qualcomm.com>
Reviewed-by: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>
Link: https://patch.msgid.link/20250411060154.1388159-5-praneesh.p@oss.qualcomm.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>